This is bird note. Think of a bird sitting on its eggs keeping them warm, waiting for them to hatch.

Sounds familiar, right? But not all birds do this. Some lay their eggs underground, in geothermally heated burrows, in warm sands, or even in huge

mounds of organic material, warmed by the heat of decomposition. These birds are called megapodes, or mound builders, and they look

a bit like large chickens. There are about 20 different species, and they're found in Australia, New Guinea, and nearby islands.

The male builds the mound, which may contain tons of organic matter. Periodically, he'll poke his beak in to check the temperature,

then he'll adjust the amount of material to maintain the heat at a constant high level.

Deep below the surface are the eggs. They're larger than most, and contain a higher proportion of yolk.

After an unusually long incubation period, the eggs hatch, and the chicks claw their way to the surface. They never know their parents.

But the young megapodes are already fully feathered, and capable of flying and feeding themselves.

For Bird Note, I'm Mary McCann.

Bird Note gives you the sounds of birds every day, and you get the sights as well when you follow us on Instagram, at Bird Note Radio.